1. Field of the Invention
The present invention relates to a power control method in a data communication network.
2. Background of the Related Art
A data communication network may be described as a communication network which connects at least two computers for allowing a number of people to share data. Data communication networks typically include a local area network which connects adjacent computers at high speed and a wide area network having internal exchanges for connecting computers worldwide. Examples include a telephone network, a broadcasting network, and a computer communication network.
Data communication networks can be classified into a local area network (LAN), a wide area network (WAN), a value added network (VAN) and an integrated services digital network (ISDN) according to scale and function. A LAN is a narrow range communication network typically found in a place of business or in a building. The standard LAN includes Ethernet, Token Ring, and FDDI. The WAN is a wide area data transmission communication network which may include a few LANs. The VAN is a communication network added with a variety of information such as accumulation and supply of information, variations of a communication speed and format, and selection of a communication path. The ISDN is an integrated service digital communication network which collectively handles communication-related services such as a telephone, fax, data communication, videotex, etc.
Data communication networks often include a hub for connecting a plurality of terminals. The hub transmits downloaded data to a corresponding terminal, and uploaded data from the respective terminals to an external network through an Ethernet switch. Recently, a Powered-HUB has been proposed which can supply power to each terminal as well as transmit/receive data.
FIG. 1 is a diagram illustrating a related art Ethernet device. In this device, a Powered-HUB 13 receives data from an Ethernet switch 11, transmits the data to a user terminal, and supplies power to one of a plurality of user terminals which needs power. Here, the user terminals may include a web camera 19, an IP phone 21, and a wireless LAN access point 23. If desired, a personal computer 25 may be connected to the IP phone. The user terminals may be connected to the Powered-HUB 13 through unshielded twisted pair (UTP) cables 15 to 17 to supply data and power. Both ends of each UTP cables 15 to 17 may include RJ-45 jacks for establishing connection between the Powered-HUB and a respective user terminal. In general, Pins 1, 2, 3 and 6 of the RJ-45 jacks are used to transmit/receive data, and the other pins, namely pins 4, 5, 7 and 8, are used to supply power.
The above-described Ethernet device guarantees compatibility between the Powered-HUB and the user terminals. In this case, the Powered-HUB and the user terminals respectively have modules for confirming necessity of power and use a special protocol for mutual communication.
When the Powered-HUB and the user terminals are incompatible, external splitters must be positioned between user terminals 19, 21 and 23 and the Powered-HUB 13 as shown in FIG. 2. The external splitters are data/power splitters 27 to 29 for respectively branching data and power from the Powered-HUB, and transmitting them to each terminal through data only lines and power only lines.
The related art Ethernet device has a number of drawbacks. For example, the conventional Ethernet device requires a special module and protocol to supply power from the Powered-HUB to the user terminals. This increases the complexity of the entire system. Furthermore, in the case that the Powered-HUB and the user terminals are not compatible with each other, the data/power splitters must be installed between the Powered-HUB and the respective user terminals. This further complicates the system design and increases costs.